A known threaded closure of the kind described above includes an outer thread formed on the inlet stub of the fuel tank on which a closure cap having an inner thread can be threadably attached. A latch to prevent an inadvertent opening of the closure is provided in the region beneath the thread of the inlet stub. The latch includes latching parts which are displaceable in a direction transverse to the axis of the threaded closure such that the closure cap is secured against removal after the latching mechanism is actuated.
In arrangements of this kind, the latched position of the closure is not clearly visible to the operator because no arrangement is provided which shows the position of the latch. Further, the latching mechanism of known configurations is relatively complicated and expensive to manufacture.